Multi-purpose single-arm-support assembly and disassembly portal crane

The utility model provides a multi-purpose single-arm-support assembly and disassembly portal crane, which comprises lifting arms, a herringbone frame, guide pulleys and rollers, wherein the lifting arms rotate around a supporting rotating shaft; the supporting rotating shaft is positioned at the bottoms of the lifting arms; a top pulley is arranged on the top of each lifting arm; the herringbone frame is arranged at a position close to the bottoms of the lifting arms; the guide pulleys are arranged above a top cross beam of the herringbone frame; the rollers are positioned at positions close to the bottoms of the lifting arms; and a steel rope extends from the rollers to the top pulleys through the guide pulleys. A mode that the direction of the steel rope is changed by the top pulley of the herringbone frame is adopted in the new coiling structure, an amplitude variation mechanism is arranged rationally, and a lifting direction-change pulley point of the herringbone frame is selected properly, so that inter